Clams Fish Snails and Crustaceans - Clams, Snails, And Crustaceans

species endangered threatened listed

Clams, snails, and crustaceans are invertebrates. Clams and snails are in the phylum Mollusca. Mollusks have soft bodies usually enclosed in a thin hard shell made of calcium. The U.S. Fish and Wildlife Service uses the generic term "clam" to refer to clams and mussels, but there are physical and reproductive differences between the two creatures. In general, mussels are larger than clams and have an oblong lopsided shell, as opposed to the round symmetrical shell of the clam.

Crustaceans are a large class of creatures with a hard exoskeleton, appendages, and antennae. This class includes lobsters, shrimps, and crabs.

As shown in Table 1.2 in Chapter 1, there were 131 species of clams (including mussels), snails, and

TABLE 6.5 Listing status of West Coast steelhead populations, January 2006"Endangered Species Act Status of West Coast Salmon & Steelhead," in Salmon Populations: Snapshot of ESU Status, U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, January 19, 2006, http://www.nwrnoaa.gov/ESA-Salmon-Listings/Salmon-Populations/ (accessed February 13, 2006)

TABLE 6.5

Listing status of West Coast steelhead populations, January 2006

Speciesa

Current Endangered Species Act listing Status b

ESA listing actions under review

aThe Endangered Species Act (ESA) defines a "species" to include any distinct population segment of any species of vertebrate fish or wildlife. For Pacific salmon, National Oceanic & Atmospheric Administration (NOAA) fisheries considers an evolutionarily significant unit, or "ESU," a "species" under the ESA. For Pacific steelhead, NOAA fisheries has delineated distinct population segments (DPSs) for consideration as "species" under the ESA.

bUpdated final listing determinations for 16 salmon species were issued on June 28, 2005 (70 FR 37160). Updated final listing determinations for 10 West Coast steelhead species were issued on January 5, 2006 (71FR 834). The final "not warranted" listing determination for Oregon Coast coho salmon was announced on January 19, 2006 (71 FR 3033). On September 2, 2005, we issued final critical habitat designations for 19 West Coast salmon and steelhead species (70 FR 52488 and 52630).

cA petition to list Puget Sound steelhead was received on September 13, 2004. The species is currently under review.

SOURCE: "Endangered Species Act Status of West Coast Salmon & Steelhead," in Salmon Populations: Snapshot of ESU Status, U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, January 19, 2006, http://www.nwrnoaa.gov/ESA-Salmon-Listings/Salmon-Populations/ (accessed February 13, 2006)

Steelhead (O. mykiss)

36

Southern California

Endangered

37

Upper Columbia River

Threatened

38

Central California Coast

Threatened

39

South central California Coast

Threatened

40

Snake River basin

Threatened

41

Lower Columbia River

Threatened

42

California Central Valley

Threatened

43

Upper Willamette River

Threatened

44

Middle Columbia River

Threatened

45

Northern California

Threatened

46

Oregon Coast

Species of concern

47

Southwest Washington

Not warranted

48

Olympic peninsula

Not warranted

49

Puget Sound

Under review

• ESA listing statusc

50

Klamath Mountains province

Not warranted

TABLE 6.6 The ten listed clam, snail, and crustacean entities with the highest expenditures under the Endangered Species Act, fiscal year 2004Adapted from "Table 1. Reported FY 2004 Expenditures for Endangered and Threatened Species, Not Including Land Acquisition Costs," in Federal and State Endangered and Threatened Species Expenditures: Fiscal Year 2004, U.S. Department of the Interior, U.S. Fish and Wildlife Service, January 2005, http://www.fws.gov/endangered/expenditures/reports/FWS%20Endangered%20Species%202004%20Expenditures%20Report.pdf (accessed February 11, 2006)

TABLE 6.6

The ten listed clam, snail, and crustacean entities with the highest expenditures under the Endangered Species Act, fiscal year 2004

Ranking

Entity

Category

Listing⟩

Expenditure

⟩E=endangered, T=threatened.

SOURCE: Adapted from "Table 1. Reported FY 2004 Expenditures for Endangered and Threatened Species, Not Including Land Acquisition Costs," in Federal and State Endangered and Threatened Species Expenditures: Fiscal Year 2004, U.S. Department of the Interior, U.S. Fish and Wildlife Service, January 2005, http://www.fws.gov/endangered/expenditures/reports/FWS%20Endangered%20Species%202004%20Expenditures%20Report.pdf (accessed February 11, 2006)

1

Higgins eye pearlymussel

Clam

E

$1,302,660

2

Vernal pool fairy shrimp

Crustacean

T

$1,018,842

3

Carolina heelsplitter

Clam

E

$991,892

4

Vernal pool tadpole shrimp

Crustacean

E

$665,972

5

Oahu tree snail

Snail

E

$613,532

6

Riverside fairy shrimp

Crustacean

E

$542,464

7

Utah valvata snail

Snail

E

$481,764

8

Clubshell (except where listed as experimental populations)

Clam

E

$475,560

9

Pink mucket peralymussel

Clam

E

$366,725

10

San Diego fairy shrimp

Crustacean

E

$311,484

crustaceans listed under the ESA as endangered or threatened as of February 2006. Most imperiled are clams/mussels (seventy U.S. species and two foreign species). There were thirty-six U.S. species of snails and one foreign species listed under the ESA. Listed crustaceans include twenty-two U.S. species. Table 6.6 shows the ten clam, snail, and crustacean entities with the highest expenditures under the ESA during fiscal year 2004.

The vast majority of imperiled clams/mussels, snails, and crustaceans in the United States are freshwater species that inhabit inland rivers, primarily in the Southeast.

Freshwater Mussels in the United States

Mussels are bivalved (two-shelled) creatures encased in hard hinged shells made of calcium. The freshwater species can grow to be up to six inches in length. The United States, with nearly 300 species, has the greatest diversity of freshwater mussels in the world. According to the U.S. Geological Survey (USGS) (March 2006, http://cars.er.usgs.gov/Southeastern_Aquatic_Fauna/Freshwater_Mussels/freshwater_mussels.html), approximately 90% of these creatures live in southeastern states. Most of them are found burrowed into the sand and gravel beds of rivers and streams making up the Mississippi River system. Mussels have a foot-like appendage that acts like an anchor to hold them in place. They can use this appendage to move themselves very slowly over small distances. Mussels tend to congregate in large groups called colonies.

Mussels are filter-feeders. They have a siphoning system that sucks in food and oxygen from the water. Their gills can filter impurities out of the water. Thus, mussels are tiny natural water purifiers.

Most mussel species have a unique way of spreading their offspring. A female mussel can produce several thousand eggs in a year. After the eggs are fertilized they develop into larva and are released. The larva latch on to the fins or gills of passing fish and they stay there until they have grown into baby clams. At that point they turn loose of the fish and drop to the river bottom. The larvae are called glochidia. It is believed that glochidia are harmless to the fish upon which they hitchhike. This parasitic relationship allows mussels to spread and distribute beyond their usual range.

MUSSEL DECLINES

Unfortunately, many freshwater mussel populations are in danger of extinction. Information about the seventy U.S. species of endangered and threatened clams and mussels as of February 2006 is shown in Table 6.7. Nearly $7.3 million was spent under the ESA during fiscal year 2004 to protect clams and mussels. Just over $1.3 million of this money was devoted to the Higgins' eye mussel, a species found in the Midwest.

The decline of freshwater mussels began in the 1800s. Many of the creatures have an interior shell surface with a pearl-like sheen. These pearlymussels were in great demand as a source of buttons for clothing until the invention of plastic. Collectors also killed many mussels by prying them open looking for pearls. Until the 1990s mussel shells were ground up and used in the oyster pearl industry. Another cause for decline has been habitat disturbance, especially water pollution and the modification of aquatic habitats by dams. The invasive zebra mussel has also harmed native freshwater mussel species by competing with them for food and other resources.

ZEBRA MUSSELS—AN INFESTATION

In 1988 an unwelcome visitor was discovered in the waters of Lake St. Clair, Michigan—a zebra mussel. The zebra mussel is native to eastern Europe. It is smaller than the freshwater mussels found in the United States and has a different method for spreading its young. The larva of zebra musses do not require a fish host to develop into babies. They can attach to any hard surface under the water. This allows zebra mussels to spread much easier and quicker than their American counterparts.

It is believed that the first zebra mussels migrated to the United States in the ballast water of ships. This is water held in large tanks below deck to improve the stability and control of ships. Ballast water is pumped in and out as needed during a journey. Zebra mussels have also been found clinging to the hulls of small fishing and recreation boats. These boats are hauled overland on trailers, and this allows the creatures to travel great distances between inland water bodies.

Figure 6.8 shows a USGS map of zebra mussel distribution around the country as of June 2005. Since 1988 this invasive species has spread dramatically from the Great Lakes south to the Gulf of Mexico and east to New England. Zebra mussels have been found on boat hulls as far west as California. Throughout waterways in the Midwest, colonies of zebra mussels have clogged pipes and other structures used for municipal and industrial water supply. In addition, the pests have significantly degraded native mussel colonies by competing for available food, space, and resources.

HIGGINS' EYE PEARLYMUSSEL

Figure 6.9 illustrates Higgins' eye, a species of freshwater pearlymussel native to the United States. These mussels are found in the waters of Iowa, Illinois, Minnesota, Missouri, Nebraska, and Wisconsin. The species was named after its discoverer, Frank Higgins, who found some of the mussels in the Mississippi River near Muscatine, Iowa, during the mid-1800s. Over the next few decades Muscatine developed a thriving pearl-button industry that lasted into the 1940s. Higgins' eye was also harvested for the commercial pearl industry.

In 1976 the Higgins' eye pearlymussel was listed as an endangered species under the ESA. More than a century of scavenging by humans had severely depleted the species. Dams, navigational structures, and water quality problems in the upper Mississippi river system were contributing factors to its decline. In 1983 the FWS published its first recovery plan for the Higgins' eye. The plan identified areas deemed essential habitat for the species and called for limits on construction and harvesting in these areas. Since 2000 scientists have collected and relocated hundreds of Higgins' eye mussels. Fish raised in hatcheries have been artificially infested with glochidia and released into rivers to enhance the spread of the mussel.

In 2004 a revised recovery plan was issued for the Higgins' eye pearlymussel. The new plan examines more recent threats to species survival, primarily the pervasive spread of zebra mussels. It acknowledges that there is no currently feasible way to eliminate zebra mussels to the extent needed to benefit the Higgins' eye. Instead, the plan focuses on development of methods to prevent new zebra mussel infestations and working to lessen the impacts of already infested populations.

CLAM/MUSSEL RECOVERY PLANS

All seventy species of clams and mussels listed under the Endangered Species Act as of February 2006 have recovery plans in draft or final form, as shown in Table 6.7. Conservation efforts for freshwater mussels include the captive breeding and reintroduction of some species, as well as measures to restore damaged habitats.

Snails

Snails belong to the class Gastropoda of mollusks. Snails typically have an external spiral-shaped shell and a distinct head that includes sensory organs. Snails inhabit terrestrial (land), marine, and freshwater

TABLE 6.7 Endangered and threatened clams, U.S. species, February 2006

Endangered and threatened clams, U.S. species, February 2006 [CONTINUED]

Population

Scientific name

Listingb

Recovery plan date

Recovery plan stagec

aEnitire range, except where listed as experimental populations.

bE=endangered; T=threatened.

cRecovery plan stages: F=final, D=draft, RF=final revision.

SOURCE: Adapted from "Listed FWS/Joint FWS and NMFS Species and Populations with Recovery Plans (Sorted by Listed Entity)" and "Listed U.S. Species by Taxonomic Group," in Threatened and Endangered Species System (TESS), U.S. Fish and Wildlife Service, February 10, 2006, http://ecos.fws.gov/tess_public/SpeciesRecovery.do?sort=1 and http://ecos.fws.gov/tess_public/SpeciesReport.do?kingdom=V&listingType=L (accessed February 17, 2006

As of February 2006 there were thirty-six U.S. species of snails and one foreign species listed under the ESA. (See Table 6.8 for a list of the U.S. species). Snails are found throughout the United States. Most imperiled species are located in western states (including Hawaii) and the Southeast (primarily Alabama). Nearly $2.4 million was spent under the ESA during fiscal year 2004 to conserve snail populations in the United States. Almost half of this money was devoted to only two species—Oahu tree snails ($613,532) and Utah valvata snails ($481,764).

OAHU TREE SNAILS

Oahu tree snails belong to the genus Achatinella and are endemic to the Oahu island of Hawaii. All forty-one species in the genus are imperiled and are collectively known as Oahu tree snails. These snails were listed as endangered under the ESA in 1981. The snails live in mountainous forests and shrublands and feed on fungi growing on the leaves of native plants. The spread of nonnative vegetation and invasive carnivorous (meat-eating) snails has seriously depleted populations of Oahu tree snails. They are also preyed upon by rats.

In 1992 the FWS released a final recovery plan for the surviving species of Achatinella in Oahu. The plan designated areas of essential habitat and called for captive propagation of the snails.

UTAH VALVATA SNAILS

Utah valvata snails were listed as endangered under the ESA in 1992. They are one of five species known as the Snake River snails that inhabit the middle portion of the Snake River in southern Idaho. All five species require cold, clean flowing water with high oxygen levels and low turbidity (suspended sediment) content. Unfortunately their habitat has been changed considerably over the past few decades by the construction of dams on the river for production of hydroelectric power. These dams have altered the flow and temperature of the river waters. Surviving Utah valvata snails are found in the mainstem of the Snake River and in tributaries fed by cold-water springs.

A recovery plan for the endangered snail has been in effect since 1995. The plan notes that the Utah valvata snail has a high degree of threat and a low degree of recovery potential. Restoration of habitat and water quality is indicated as the only means for saving the snail from extinction.

In late 2003 Utah valvata snails were discovered on a bridge being demolished near Firth, Idaho. Prior to that that time the species had not been found that far south in the Snake River. The Idaho Transportation Department suspended the demolition project so that biologists could conduct a survey of the snails. In 2004 the FWS announced that bridge removal could continue because it did not pose a threat to the survival of the species at that location. However, the discovery of the snails is expected to affect other construction projects planned for that part of the river.

RECOVERY PLANS FOR SNAILS

Table 6.8 lists the snail species for which recovery plans have been published as of February 2006. Two of the species that do not have plans—Pecos assiminea snails and Roswell springs-nails—were listed under the ESA during 2005. The white abalone snail is under the jurisdiction of the National Marine Fisheries Service. It is a marine snail that inhabits deep waters off the coast of Southern California.

Crustaceans

Crustaceans are a large class of mandibulate (jawed) creatures in the phylum Arthropoda. They are mostly aquatic and inhabit marine and fresh waters. As of February 2006 there were twenty-two U.S. species listed as endangered or threatened under the Endangered Species Act as shown in Table 6.9. They are found throughout the United States. However, California is home to more imperiled crustacean species than any other state.

More than $2.8 million was spent under the ESA during fiscal year 2004 on endangered and threatened crustaceans. Just over $1 million of these expenditures was devoted to the vernal pool fairy shrimp.

VERNAL POOL FAIRY SHRIMP

The vernal pool fairy shrimp was listed under the ESA as threatened in 1994. It is found in California and Oregon. Vernal is from the Latin word for "spring." This species inhabits temporary small ponds and pools of water that appear in the springtime and dry up after a time. The shrimp lay their eggs in these pools when they contain water. The eggs can go dormant in the dirt when the pools become dry. Baby shrimp hatch only when exposed to water at less than
TABLE 6.8 Endangered and threatened snail species in the United States, February 2006Adapted from "Listed FWS/Joint FWS and NMFS Species and Populations with Recovery Plans (Sorted by Listed Entity)" and "Listed U.S. Species by Taxonomic Group," in Threatened and Endangered Species System (TESS), U.S. Department of the Interior, U.S. Fish and Wildlife Service, February 17, 2006 http://ecos.fws.gov/tess_public/SpeciesRecovery.do?sort=1 and http://ecos.fws.gov/tess_public/SpeciesReport.do?kingdom=I&listingType=L (accessed February 17, 2006)approximately 50° Fahrenheit. Adults typically reach 0.4 to 1 inch in length. The shrimp have a lifetime of two to five months.

TABLE 6.8

Endangered and threatened snail species in the United States, February 2006

SOURCE: Adapted from "Listed FWS/Joint FWS and NMFS Species and Populations with Recovery Plans (Sorted by Listed Entity)" and "Listed U.S. Species by Taxonomic Group," in Threatened and Endangered Species System (TESS), U.S. Department of the Interior, U.S. Fish and Wildlife Service, February 17, 2006 http://ecos.fws.gov/tess_public/SpeciesRecovery.do?sort=1 and http://ecos.fws.gov/tess_public/SpeciesReport.do?kingdom=I&listingType=L (accessed February 17, 2006)

Alamosa springsnail

Tryonia alamosae

E

8/31/1994

F

Anthony's riversnaila

Athearnia anthonyi

E

8/13/1997

F

Armored snail

Pyrgulopsis (=marstonia) pachyta

E

7/1/1994

D

Banbury Springs limpet

Lanx sp.

E

11/26/1995

F

Bliss Rapids snail

Taylorconcha serpenticola

T

11/26/1995

F

Bruneau hot springsnail

Pyrgulopsis bruneauensis

E

9/30/2002

F

Chittenango ovate amber snail

Succinea chittenangoensis

T

12/5/2003

RD(1)

Cylindrical lioplax (snail)

Lioplax cyclostomaformis

E

12/2/2005

F

Flat pebblesnail

Lepyrium showalteri

E

12/2/2005

F

Flat-spired three-toothed snail

Triodopsis platysayoides

T

5/9/1983

F

Idaho springsnail

Fontelicella idahoensis

E

11/26/1995

F

Iowa pleistocene snail

Discus macclintocki

E

3/22/1984

F

Kanab ambersnail

Oxyloma haydeni kanabensis

E

10/12/1995

F

Lacy elimia (snail)

Elimia crenatella

T

12/2/2005

F

Magazine Mountain shagreen

Mesodon magazinensis

T

2/1/1994

F

Morro shoulderband (=banded dune) snail

Helminthoglypta walkeriana

E

9/28/1998

F

Newcomb's snail

Erinna newcombi

T

3/24/2004

D

Noonday snail

Mesodon clarki nantahala

T

9/7/1984

F

Oahu tree snails

Achatinella spp.

E

6/30/1992

F

Painted rocksnail

Leptoxis taeniata

T

12/2/2005

F

Painted snake coiled forest snail

Anguispira picta

T

10/14/1982

F

Pecos assiminea snail

Assiminea pecos

E

None

—

Plicate rocksnail

Leptoxis plicata

E

12/2/2005

F

Round rocksnail

Leptoxis ampla

T

12/2/2005

F

Roswell springsnail

Pyrgulopsis roswellensis

E

None

—

Royal marstonia (snail)

Pyrgulopsis ogmorhaphe

E

8/11/1995

F

Slender campeloma snail

Campeloma decampi

E

None

—

Snake River physa snail

Physa natricina

E

11/26/1995

F

Socorro springsnail

Pyrgulopsis neomexicana

E

8/31/1994

F

Stock Island tree snail

Orthalicus reses (not including nesodryas)

T

5/18/1999

F

Stock Island tree snail

Orthalicus reses (not including nesodryas)

T

4/2/2004

O

Tulotoma snail

Tulotoma magnifica

E

11/17/2000

F

Tumbling Creek cavesnail

Antrobia culveri

E

9/22/2003

F

Utah valvata snail

Valvata utahensis

E

11/26/1995

F

Virginia fringed mountain snail

Polygyriscus virginianus

E

5/9/1983

F

White abalone snail

Haliotis sorenseni

T

None

—

In 2003 critical habitat was designated for the vernal pool fairy shrimp along with several other species of vernal pool shrimp. During 2004 a draft recovery plan was issued by the U.S. Fish and Wildlife Service for dozens of imperiled plant and animal species that inhabit vernal pool ecosystems in California and southern Oregon. The plan notes that vernal pool life forms are threatened by urban and agricultural development and invasion of nonnative species. The recovery of vernal pool species will require an ecosystem-wide approach. The FWS proposes establishing conservation areas and reserves to protect primary vernal pool habitat.

CRUSTACEAN RECOVERY PLANS

As shown in Table 6.9 nearly all endangered and threatened species of crustaceans found in the United States had recovery plans as of February 2006. Most plans were in final form. Two listed species (Hay's spring amphipod and squirrel chimney cave shrimp) are exempt from the requirement for a recovery plan.

Imperiled Mollusks and Crustaceans around the World

The IUCN listed 974 species of mollusks and 429 species of crustaceans as threatened in its 2004 IUCN Red List of Threatened Species (2004, http://www.redlist.org/). For mollusks, this number comprises 45% of the 2,163 species evaluated. The IUCN reports that approximately 70,000 mollusk species are known. Only 498 crustacean species were evaluated for the 2004 report. Threatened species comprise 86% of this total. However, the IUCN notes that there are approximately 40,000 known species of crustaceans.

TABLE 6.9 Endangered and threatened crustacean species in the United States, February 2006Adapted from "Listed FWS/Joint FWS and NMFS Species and Populations with Recovery Plans (Sorted by Listed Entity)" and "Listed U.S. Species by Taxonomic Group," in Threatened and Endangered Species System (TESS), U.S. Department of the Interior, U.S. Fish and Wildlife Service, February 17, 2006, http://ecos.fws.gov/tess_public/SpeciesRecovery.do?sort51 and http://ecos.fws.gov/tess_public/SpeciesReport.do?kingdom5I&listingType5L (accessed February 17, 2006)

TABLE 6.9

Endangered and threatened snail species in the United States, February 2006

SOURCE: Adapted from "Listed FWS/Joint FWS and NMFS Species and Populations with Recovery Plans (Sorted by Listed Entity)" and "Listed U.S. Species by Taxonomic Group," in Threatened and Endangered Species System (TESS), U.S. Department of the Interior, U.S. Fish and Wildlife Service, February 17, 2006, http://ecos.fws.gov/tess_public/SpeciesRecovery.do?sort51 and http://ecos.fws.gov/tess_public/SpeciesReport.do?kingdom5I&listingType5L (accessed February 17, 2006)

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